This article discusses why copying files between disks on a Windows Cloud Server will occasionally get stuck at 99%

Issues Reported by Users

Issue Reported
Copying Files between Disks stays at 99% for a while before completionWhen Disk Cache is enabled, the data will be sitting on the cache until it can be accommodated by the underlying Storage. The throughput of the underlying Storage plays a major role before the commit is completed. For example, if you are writing a 1 GB file to a disk, it will be cached before its committed and if you have 1000 Kbps of throughput - that throughput will be used during the commit function.
Disk freezes during file copy when low IOPS is assigned.As mentioned above, if the throughput is minimal and not enough for the commit operation, the disk might freeze for a few seconds to a few minutes (based on the file size) before the commit is completed.

The solution is to disable Disk Cache on the Cloud Server.

Disk write caching is designed to speed up system processes and applications by allowing them to proceed without waiting for data to be written to the disk. In other words, it enables them to continue operating, while in fact the data are still sitting in the cache and waiting until the underlying storage can accommodate it. That is, the write request is getting acknowledged once the actual data is placed on cache instead of on to the targeted device.

Windows Cloud Servers have Disk Cache enabled by default. This article explains how to disable Disk Cache on a Windows Cloud Server.

Note: In this example, we are using Windows Server 2012 R2. The procedure for disabling Disk Cache is slightly different, depending upon the version of Windows. However, once you navigate to Device Manager, the process is exactly the same.

Procedure to Disable Disk Cache on a Windows Cloud Server

  1. Console into the Windows Server. 

    Note: For instructions on how to gain Console access, see How to Get Virtual Console Access to a Cloud Server

  2. Once the Console session is established, navigate to Device Manager:

    Note: The process for arriving at Device Manager is different depending on the version of Windows

  3. Expand the Disk Drives tab:

  4. Locate the Disk on which you want to disable Disk Caching, then right-click, and select Properties:

  5. Click on the Policies tab:

  6. Select "Quick Removal" for Disabling Write Cache and Click OK to apply: